1. Field of the Invention
The invention relates to an electronic-switching component with field-effect transistors on a gallium-arsenide-based substrate, which is used especially but not exclusively for rapid switching of high-frequency signals in microwave attenuation circuits, and which can be irradiated by a light source, wherein the light irradiating the field-effect transistors can substantially shorten the switching times of the field-effect transistors and/or of the electronic-switching component.
2. Related Technology
It is already known that field-effect transistors can be used very readily on a semiconductor chip. Moreover, they require only very little control power. One consequence of illuminating gallium-arsenide-based field-effect transistors, especially MESFETs, is that imperfections occurring at the semiconductor junctions especially below the gate electrode, which have a negative influence on the switching times of the field-effect transistors, are recharged more rapidly. The negative influence of imperfections in MESFET components is known as the gate-lag effect and can be measured as an extremely slow change in the bulk resistance. This is caused by the slow charging and discharging of the surface imperfections of the source-gate path and the gate-drain path. Illuminating the field-effect transistors generates electron-hole pairs, which neutralise the charges trapped in the imperfections. Illumination can be used to suppress the gate-lag effect and to shorten the switching time by a factor of 10-100.
High-frequency circuits, such as microwave circuits, which are designed as attenuation circuits, can be used, for example, in high-frequency technology for measuring purposes, for example, for controlling the level of signal generators and network analysers. For example, in order to implement measurement series with different variable parameters rapidly, the attenuation circuits and/or the switching components used in them must be able to switch very rapidly and must provide a very wide dynamic range. Circuits with gallium-arsenide-based field-effect transistors, which, in more recent switching arrangements, can be additionally illuminated, are used in this context especially in order to achieve a further shortening of the switching-time, in particular, because of their excellent high-frequency compatibility and their very-short switching times.
DE 102 28 810 A1 discloses a generic microwave circuit. The digitally-controllable attenuation element disclosed in this document is built up with field-effect transistors as the switching elements, which can be illuminated, for example, by an LED. In this context, the circuit of field-effect transistors is built up on an un-housed, gallium-arsenide semiconductor chip, wherein the semiconductor chip is attached to a substrate using a costly and difficult hybrid technique and connected to the substrate by electrical connections. The semiconductor chip does not have its own, dedicated housing, because the light from the light source must irradiate the field-effect transistors. Accordingly, the microwave circuit disclosed in the named document is enclosed in a cost-intensive manner within an air-tight housing.
The disadvantage with the electronic-switching component with field-effect transistors on a gallium-arsenide-based substrate disclosed in DE 102 28 810 A1 is that a difficult, cost-intensive and sensitive assembly technique, a so-called hybrid technique, must be used to attach and contact the switching component in a circuit, because the switching component does not have its own housing, which provides, for example, its own contact terminals (pins) leading to the outside. Moreover, in order to protect the sensitive, open switching component and/or the semiconductor junctions or metal-semiconductor junctions from environmental influences and dust particles, which can, for example, cause shadows at a semi-conductor junction, the switching component and the substrate, to which the switching component is attached, is surrounded by a large-volume, air-tight and correspondingly cost-intensive housing.